Web tension control device

ABSTRACT

A web feeding device is provided having a receptacle for peripherally supporting a web supply roll, a web feeder for moving a web past a print station or the like upon demand and a web tension control device mounted therebetween for supplying web from the former to the latter. The web tension control device has a pressure roller pivotable to press a passing web effectively against a continuously rotatable friction roller in response to an increase in web tension as detected by a lever contacting the web and operatively coupled to the pressure roller.

United States Patent Frederick et al.

1451 Dec. 5, 1972 154] WEB TENSION CONTROL DEVICE [72] lnventors: HaroldM. Frederick, Birmingham; Dewey M. Sims, Jr., Westland, both of Mich.

[73] Assignee: Burroughs Corporation, Detroit,

Mich.

[22] Filed: May3, 1971 [211 Appl. No.: 139,602

[52] US. Cl. ..226/34, 226/44, 242/68.7 [51] Int. Cl. ..B65h 25/04 [58]Field of Search .....226/25, 34, 35, 44; 242/68.7,

[5 6] References Cited UNITED STATES PATENTS 1,586,719 6/1926 Swab..226/34 2,990,989 7/1961 Carlson ..226/35 Primary Examiner-Richard A.Schacher Attorney-Kenneth L. Miller and Edwin W. Uren [5 7 ABSTRACT Aweb feeding device is provided having a receptacle for peripherallysupporting a web supply roll, a web feeder for moving a web past a printstation or the like upon demand and a web tension control device mountedtherebetween for supplying web from the former to the latter. The webtension control device has a pressure roller pivotable to press apassing web effectively against a continuously rotatable friction rollerin response to an increase in web tension as detected by a levercontacting the web and operatively coupled to the pressure roller.

9 Claims, 2 Drawing Figures PATENT-ED "EC 5 I97? 3 704,820 sum 1 OF 2mvszv'rons HAROLD M. FREDERICK BY DEWEY M. SIMS JR.

PATENTEU 5 I97? 3.704.820

sum a nr 2 WEB TENSION CONTROL DEVICE BACKGROUND OF THE INVENTION Theinvention relates generally to web feeding devices and more particularlyto web tension controlling devices used in conjunction therewith.

Prior art discloses devices for controlling web tension by damping webdrag variations. A first type of device uses resiliently biased leversresponsive to slack loops in the web to damp variations in web tensionand thereby provide more uniform feed. Similar devices use resilientlybiased idler rollers or combinations of resiliently biased levers andidler rollers to obtain uniform feed. Devices of this type provide norelief from web drag for the web feeders other than by tending tostabilize the values of the drag. Indeed, by virtue of their ownintrinsic friction, they add to the total amount of web drag which mustbe overcome by the web feeders.

A second type of device uses gravitationally or resiliently biased,class-one levers to provide a more uniform feed. These exert brakingforces on axially supported web supply reels upon decreases in webtension and release the reels to rotate freely upon increases in webtension. Devices of this type also provide no relief from web drag forthe web feeders, except as noted previously, and also add to the totalamount of web drag which must be overcome by the web feeders. Inaddition, these devices require some type of axial support for websupply rolls; and this results in more costly manufacturing andmaintenance and inconvenience in replacing the supply rolls.

A third type of device disclosed by prior art uses a resiliently biased,class-two lever responsive to a slack loop in the web to actuate aswitch controlling an auxiliary web driver. When web slack is reduced toa certain amount by the action of the web feeder, the auxiliary webdriver is actuated until the web is overdriven with respect to thefeeder by a predetermined amount, whereupon the auxiliary driver isdisengaged until the web slack loop has again been depleted by thefeeder. Devices of this type require additional components forcontrolling the auxiliary web drivers, thus inflating the manufacturingand maintenance costs and increasing the probability of operationalmalfunctions.

A fourth type of device uses a resiliently biased, class-two leverpivotable by a diminishing web loop by virtue of the stiffness of theweb to thereby force the web against a rotating friction roller. Suchdevices find suitable application in cinematographic equipment whereinthe web being fed is typically motion picture film having a relativelyhigh degree of stiffness. The same principle would not be readilyapplicable to feeding more pliant, flexible webs. In addition, thenormal force holding the web against the friction roller is that derivedfrom the web tension and applied by the lever against the force of itsown resilient bias. Since the driving force exerted on the web by thefriction roller is equal to the product of this normal force and of thecoefficient of friction, which is always less than unity, existingbetween the roller and the web, the driving force is thus limited.

SUMMARY OF THE INVENTION The invention resides in the provision of anactuatable web driver responsive to web tension for driving a web in thedirection of a web feeder, thereby relieving the latter of a substantialportion of the drag inherent in a web feeding device.

Accordingly, it is an object of the present invention to provide a webtension control device which will relieve a feeder of a substantialamount of web drag, particularly that component arising from theinertial force of the heavy web supply roll.

It is another object of the invention to provide a web feeding devicewhich will receive and peripherally support a web supply roll, no axialsupport being required, thus providing for a relatively simple supplyroll changing procedure.

It is yet another object of the invention to provide a web tensioncontrol device requiring a minimum of components, the control devicebeing effectively selfactuated by web tension variations.

It is still another object of the invention to provide a web feedingdevice which will direct a newly inserted web to the web feeder withoutmanual threading.

Another object of the invention is to provide a web feeding device foruse in a printing apparatus wherein the shape of the platen used may beeither flat or curved.

Still another object of the invention is to provide a web feeding devicewhich will readily accept webs of varying stiffness, thickness andnumbers of layers.

Yet another object of the invention is to provide a web feeding devicewhich will allow manual actuation of the web tension control mechanism.

An important aspect of the invention is the use of a pair of magnets formagnetically biasing the web tension control device in either one of twopositions.

Another important aspect of the invention is the use of a resilientmaterial to form a lever actuating the web tension control device, thuspermitting the lever to flex in response to variations in web tension,thereby accumulating energy in proportion to lever displacement forrapidly transferring the web tension control device from one to theother of its two magnetically biased positions in response to asufficient change in web ten- SIOII.

BRIEF DESCRIPTION OF THE DRAWINGS These and other objects, aspects andadvantages of the invention will be more clearly understood from thefollowing description when read in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a partially fragmented, perspective view of a web feedingdevice embodying features of the invention; and

FIG. 2 is a side view of the device of FIG. 1, shown with one side plateremoved therefrom.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION The webfeeding device shown in FIGS. 1 and 2 has a support structure or frame,generally indicated at 10, a web supply roll receptacle, generallyindicated at 12, a web feeder, generally indicated at 14, an actuatableweb driver, generally indicated at 16, and web driver control, generallyindicated at 18. The receptacle is mounted on the frame, spaced apartfrom the feeder; and the driver and driver control are mountedeffectively therebetween.

The frame has a horizontally disposed base plate 20 and a pair ofupright side plates 22-22, one of which is not shown in FIG. 2, eachextending upwardly from an opposing edge of the base plate. Extendingbetween the side plates is a V-shaped plate 24, it being supported byand at the same time serving to reinforce the side plates. The shape ofthe plate 24 enables it to function as a web supply roll receptacle 12,its sloping, interior surface providing peripheral support for a roll26. The edge of the receptacle plate extending toward what willhereinafter be referred to as the forward end of the web feeding deviceis downwardly arcuated to form a smooth lip 28 over which a passing web30 may be freely guided.

The web feeder 14 is represented in this embodiment by a rotatable feedroller 32 journaled in and extending perpendicularly between the sideplates 22-22 near the forward end of the web feeding device and apressure roller 34 effectively overlying the feed roller. It should beunderstood, however, that any suitable type of web feeder could be usedwithout departing from the scope of the invention. As previously stated,one of the objects of this invention is to provided a web feeding devicein which may be used either a flat or a curved platen. An elongatedplaten 36 having a flat surface is shown for the sake of illustration.Like the web feeder it underlies, it extends perpendicularly between theside plates, its impression surface being coplanar with the path the webfollows as it is drawn toward the feeder.

A V-shaped guide plate 38 is supported between the side plates, forwardof the receptacle plate 24. Like the latter, it also serves to reinforcethe side plates. The rearward edge of the guide plate is spaced apartfrom the receptacle 12, leaving an elongated opening therebetween; andthe plane of the guide surface extending therefrom is tangent to theouter surface of the downwardly arcuated edge of the receptacle plate.The shape of the guide plate enables it to function as a guide to directa web driven from the receptacle toward the platen 36 and web feeder 14.The forward edge of the guide plate is curved downwardly to form asmooth lip past which a web may be freely drawn.

The actuatable web driver 16 has a continuously rotatable frictionroller 40 journaled in and extending perpendicularly between the sideplate such that it is disposed in the elongated opening between theforward edge of the receptacle plate 24 and the rearward edge of theguide plate 38 and is slightly, peripherally recessed from the adjacentplane of the guide plate. The web driver control 18 is pivotallysupported by and is slidable along a shaft 42 extending between the sideplates parallel to and spaced apart from the friction roller. A webdriver pressure roller 44 is rotatably mounted on the control such thatit is rockable effectively toward or way from the friction roller as thecontrol is pivoted about its axis. The control has a lever 46 extendingtherefrom and along the downwardly sloping portion of the guide plate38, the free end falling just short of the upwardly sloping portionthereof. The lever is formed of a resilient material, which will permitflexing thereof; and its free end is curved upwardly to form a smooth,arcuate surface around which a web may be freely drawn. The innerportion of the curved lever end houses a weight 48 which is normallysufficient to pivot the control 18 such that the pressure roller 44attached thereto will be swung away from the friction roller 40.

A pair of elongated limit plates 50-50 extends perpendicularly betweenthe side plates and overlies the web driver control 18. An arm 52extends upwardly from the control and passes between and somewhat beyondthe two limit plates. The opposing surfaces of the two limit plates arecoplanar with those of the arm as it swings from one respective plate tothe other when the control is pivoted. One of a pair of elongatedmagnets 54-54 is disposed on each of the limit plates to effectivelybias the arm thereagainst, the arm being formed of a magneticallyattractable material.

OPERATION OF THE INVENTION The web feeding device may be loaded byplacing a web supply roll 26 into the receptacle 12 as shown in FIGS. 1and 2. The roll requires no axial support but simply rests peripherallyon the V-shaped receptacle plate 24. The leading edge of the web 30 isthen inserted into the web driver 16 between the friction roller 40 andthe pressure roller 44 thereof. The leading edge needs no specialpreparation, such as being cut squarely, but can merely be that edgeformed when a previous length of web was manually separated. Also, theweb thickness may vary; or the web may be formed of several individuallayers. After the web has been inserted between the rollers, the arm 52,which has until this time been positioned as indicated by the brokenlines in FIG. 2 under the influence of gravity acting on the lever 46and the mass 48, is manually moved to its rearwardmost position asindicated by the solid lines in the same figure. As the arm is movedrearwardly, the web driver control 18 pivots in a counterclockwisedirection, as viewed, around the shaft 42, rocking the pressure roller44 against the friction roller 40 and pinching the inserted webtherebetween. Since the friction roller is continuously rotating in aclockwise direction as viewed, the web will be drivern forwardlythereby. As the web is driven forwardly, it will follow the contour ofthe guide plate 38, passing under the extended lever 46 and movingupwardly to emerge just below the platen 36. Once a suitable length ofweb has been driven through, the leading edge may then be fed into theweb feeder 14 between the feed roller 32 and the pressure roller 34. Inthe feeder embodiment shown for the sake of illustration, this would bedone manually; but, in a slightly more sophisticated embodiment, the webcould be automatically guided through the feeder, for example, by simplyextending and suitably forming the guide plate 38. Also, in a moresophisticated embodiment, the arm 52 could be operatively connected to aconvenient operating lever on or near the front of the device.

After the device has been loaded as previously described, the lever 46,arm 52 and pressure roller 44 will be positioned as indicated by thebroken lines in FIG. 2. As the feeder 14, upon demand, advances the web30 past the platen 36, the slack loop in the web formed above the guideplate 38 will be reduced. As the web becomes more taut, the free end ofthe lever will be raised, flexing the body of the lever since the arm isheld forward by one of the magnets 54. When the counterclockwise forceexerted on the driver control 18 due to increasing web tension acting onthe lever exceeds the clockwise force exerted on the driver control dueto the magnetic attraction acting on the arm, the arm will pivotrearwardly. The arm will continue to be driven rapidly in thisdirection, until it abuts the rearwardmost limit plate 50, under theinfluence of the restoring force of the flexed lever 46 and terminallyunder the influence of the magnet 54 mounted on the limit plate towardwhich it is moving, the arm subsequently being held thereagainst by thismagnet.

As the driver control 18 is pivoted in a counterclockwise direction, thepressure roller 44 is swung toward the recessed periphery of thefriction roller 40, pressing the web thereagainst. The ratio of thelengths of the lever 46 and of the arm 52 with respect to the distancebetween the rotational axis of the pressure roller and the pivotal axisof the driver control is large enough to provide a suitable mechanicaladvantage such that the normal force pressing the web against thefriction roller is adequate for driving the web therewith.

As the web 30 is driven by the friction roller 40, a slack loop is againformed in the web above the guide plate 38. The lever 46, once supportedby the web in the raised position indicated by the solid lines in H0. 2,will swing downward under the influence of gravity acting on the leverand on the weight 48 attached to its free end, flexing the body of thelever in this direction since the arm 52 is held rearward by one of themagnets 54. When the clockwise force exerted on the driver control 18due to decreasing web tension acting on the lever exceeds thecounterclockwise force exerted on the driver control due to the magneticattraction acting on the arm, the arm will pivot forwardly. The arm willcontinue to be driven rapidly in this direction, until it abuts theforwardmost limit plate, under the influence of the restoring force ofthe flexed lever and terminally under the influence of the magnetmounted on the limit plate toward which it is moving, the armsubsequently being held thereagainst by this magnet. As the drivercontrol 18 is pivoted in a clockwise direction, the pressure roller 44is swung away from the recessed periphery of the friction roller 40,releasing the web being held thereagainst. At this time, the lever, armand pressure roller will again be positioned as indicated by the brokenlines in FIG. 2. The components of the web feeding device will remain inthis position until such time as a demand upon the web feeder reducesthe web slack loop sufficiently to transfer the arm to the rearwardmostlimit plate, initiating another cycle of operation as previouslydescribed.

While the web feeding device has been shown and described inconsiderable detail, it should be understood that many changes andvariations may be made therein without departing from the spirit andscope of the invention.

What is claimed is:

l. A web tension control device comprising:

a support structure;

an actuatable web driver having a continuously rotatable friction rollermounted on said support structure and a pressure roller pivotableagainst said friction roller for pressing a passing web effectivelythereagainst;

a web drive control pivotally mounted on said support structure andsupporting said pressure roller,

s 'd control havin a lever extendin therefrom to e ectively contac a webbeing ed thereby to pivot said pressure roller toward or away from saidfriction roller in response to a respective increase or decrease in webtension; and

a pair of limit plates mounted on said support structure parallel to butspaced apart from said friction roller and also having an arm extendingfrom said web driver control between said plates, whereby the angulardisplacement of said control is limited.

2. A web tension control device as defined by claim 1 wherein said armoperatively extends past said limit plates, whereby provision is madefor manual actuation of said web driver.

3. A web tension control device as defined by claim 2 and additionallyhaving a pair of magnets, each disposed on a respective one of saidlimit plates for magnetically biasing said web driver in either one oftwo positions, said arm being formed of a magnetically attractablematerial.

4. A web tension control device as defined by claim 3 wherein said leveris formed of a resilient material, whereby it will be permitted to flexin response to variations in web tension.

5. A web tension control device as defined by claim 4 and additionallyhaving a weight secured to the extended end of said lever, whereby forceis provided for transferring said web driver from one to the other ofits two magnetically biased positions in response to a sufficientdecrease in web tension.

6. A web feeding device comprising:

a support structure;

V-shaped plate mounted on said support structure to form a receptaclefor receiving and peripherally supporting a web supply roll;

a web feeder mounted on said support structure spaced apart from saidreceptacle;

an actuatable web driver disposed effectively between said receptacleand said web feeder and having a continuously rotatable friction rollermounted on said support structure and a pressure roller pivotableagainst said friction roller to press a passing web effectivelythereagainst; and

a web driver control pivotally mounted on said support structure andsupporting said pressure roller, said control having a lever extendingtherefrom to effectively contact a web being fed thereby to pivot saidpressure roller toward or away from said friction roller in response toa respective increase or decrease in web tension.

7. A web feeding device as defined by claim 6 and additionally having aweb guide mounted on said support structure and forming a pathway fromsaid actuatable web driver to said web feeder, whereby a web manuallyinserted into said driver will be directed to said feeder.

8. A web feeding device as defined by claim 7 wherein said frictionroller is peripherally recessed in said web guide.

9. A web feeding device as defined by claim 8 wherein said web drivercontrol is slidable along its pivotal axis, whereby webs of differentdimensions may be effectively accommodated.

1. A web tension control device comprising: a support structure; anactuatable web driver having a continuously rotatable friction rollermounted on said support structure and a pressure roller pivotableagainst said friction roller for pressing a passing web effectivelythereagainst; a web drive control pivotally mounted on said supportstructure and supporting said pressure roller, said control having alever extending therefrom to effectively contact a web being fed therebyto pivot said pressure roller toward or away from said friction rollerin response to a respective increase or decrease in web tension; and apair of limit plates mounted on said support structure parallel to butspaced apart from said friction roller and also having an arm extendingfrom said web driver control between said plates, whereby the angulardisplacement of said control is limited.
 2. A web tension control deviceas defined by claim 1 wherein said arm operatively extends past saidlimit plates, whereby provision is made for manual actuation of said webdriver.
 3. A web tension control device as defined by claim 2 andadditionally having a pair of magnets, each disposed on a respective oneof said limit plates for magnetically biasing said web driver in eitherone of two positions, said arm being formed of a magneticallyattractable material.
 4. A web tension control device as defined byclaim 3 wherein said lever is formed of a resilient material, whereby itwill be permitted to flex in response to variations in web tension.
 5. Aweb tension control device as defined by claim 4 and additionally havinga weight secured to the extended end of said lever, whereby force isprovided for transferring said web driver from one to the other of itstwo magnetically biased positions in response to a sufficient decreasein web tension.
 6. A web feeding device comprising: a support structure;V-shaped plate mounted on said support structure to form a receptaclefor receiving and peripherally supporting a web supply roll; a webfeeder mounted on said support structure spaced apart from saidreceptacle; an actuatable web driver disposed effectively between saidreceptacle and said web feeder and having a continuously rotatablefriction roller mounted on said support structure and a pressure rollerpivotable against said friction roller to press a passing webeffectively thereagainst; and a web driver control pivotally mounted onsaid support structure and supporting said pressure roller, said controlhaving a lever extending therefrom to effectively contact a web beingfed thereby to pivot said pressure roller toward or away from saidfriction roller in response to a respective increase or decrease in webtension.
 7. A web feeding device as defined by claim 6 and additionallyhaving a web guide mounted on said support structure and forming apathway from said actuatable web driver to said web feeder, whereby aweb manually inserted into said driver will be directed to said feeder.8. A web feeding device as defined by claim 7 wherein said frictionroller is peripherally recessed in said web guide.
 9. A web feedingdevice as defined by claim 8 wherein said web driver control is slidablealong its pivotal axis, whereby webs of different dimensions may beeffectively accommodated.